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What causes coronary heart disease?

Your heart is a pump the size of a fist that sends blood around the body

Coronary heart disease (CHD) is arguably the the UK's biggest killer. CHD develops when the blood supply to the muscles and tissues of the heart becomes obstructed by the build-up of fatty materials inside the walls of the coronary arteries.

What is coronary heart disease?

Your heart is a pump the size of a fist that sends oxygen-rich blood around your body. The blood travels to the organs of your body through blood vessels known as arteries, and returns to the heart through veins.

Your heart needs its own blood supply to keep working. Heart disease occurs when the arteries that carry this blood, known as coronary arteries, start to become blocked by a build-up of fatty deposits.

The inner lining of the coronary arteries gradually becomes furred with a thick, porridge-like sludge of substances, known as plaques, and formed from cholesterol. This clogging-up process is known as atherosclerosis.

The plaques narrow the arteries and reduce the space through which blood can flow. They can also block nutrients being delivered to the artery walls, which means the arteries lose their elasticity. In turn, this can lead to high blood pressure, which also increases the risk of heart disease. This same process goes on in the arteries throughout the body, and can lead to high blood pressure which puts further strain on the heart.

If your arteries are partially blocked you can experience angina - severe chest pains that can spread across your upper body - as your heart struggles to keep beating on a restricted supply of oxygen. You are also at greater risk of a heart attack.

Some people have a higher risk of developing atherosclerosis due to genetic factors - one clue to this is a family history of heart disease in middle-age. Lifestyle factors that increase the risk include an unhealthy diet, lack of exercise, diabetes, high blood pressure and, most importantly, smoking.

However, in the past couple of decades deaths from coronary heart disease have nearly halved, thanks to better treatments.

What happens during a heart attack?

A heart attack happens when one of the coronary arteries becomes completely blocked. This usually happens when a plaque, which is already narrowing an artery, cracks or splits open. This triggers the formation of a blood clot around the plaque, and it is this blood clot that then completely blocks the artery.

With their supply of oxygen completely blocked, the heart muscle and tissue supplied by that artery start to die. Emergency medical intervention is needed to unblock the artery and restore blood flow. This may consist of treatment with drugs to dissolve the clot or thrombus, or a small operation done through the skin and blood vessels to open up the blocked artery.

The outcome of a heart attack hinges on the amount of the muscle that dies before it is corrected. The smaller the area affected, the greater the chance of survival and recovery.

While a heart attack will always cause some permanent damage, some areas may be able to recover if they are not deprived of blood for too long. The sooner a heart attack is diagnosed and treated, the greater the chance of recovery.

Other heart diseases

Other diseases that commonly affect the heart include:

Chronic heart failure - CHD is one of the main causes of heart failure. It affects around one million people in the UK, and many more have it but haven't been formally diagnosed. Here, the heart doesn't works effectively as a pump, and fluid gathers in the lower limbs and lungs. This causes a variety of symptoms and significantly reduces quality of life.

Infection - bacterial infections such as endocarditis are much rarer these days thanks to antibiotics, but can damage the valves of the heart as well as other tissues. Viral infections can damage the heart muscle leading to heart failure, or cause abnormal heart rhythms.

Congenital heart disease - a number of defects can develop in the heart as a baby grows in the womb. One example is a hole in the heart, also known as a septal defect. Congenital heart disease may cause abnormal blood flow and put excessive strain on the infant's heart after it has been born.

Cardiomyopathy - a disease of the heart muscle that can occur for different reasons, including coronary heart disease, high blood pressure, viral infection, high alcohol intake and thyroid disease.

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